A New Inductance Cancelation Scheme for Surface Mount Shunt Capacitor Filters

This article describes a new inductance cancelation scheme. The new scheme, named bilateral magnetic coupling (BMC), is applied to a surface mount shunt capacitor filter on a printed circuit board. In the filter structure, input/output paths are placed in parallel with the shunt path from a power supply trace to a ground plane. To reduce parasitic inductance of the shunt path, magnetic couplings between the input/output paths and the shunt path are utilized. The theory of BMC is explained by the method of partial equivalent elements circuit. The filter parameter design of the BMC is investigated using parametric electromagnetic simulation. When BMC performance was evaluated on a test board, it improved by 4.5 dB at 100 MHz under operation of ICs. These results show that the BMC improves the filter performance in the frequency range from a few megahertz to subgigahertz, where noise reduction is important in digital systems.